Manufacture of paper



Patented June 2, 1931 UNITED STATES PATENT-OFFICE HAROLD ROBERT RAFTON, LAWRENCE, MASSACHUSETTS, ASSIGNOR TO PROCESS CORPORATION, A CORPORATION OF MASSACHUSETTS MANUFACTURE or rerun No Drawing. Application filed November 15, 1928, Serial No. 319,720. Renewed January 21, 1981.

This invention relates to the"manufacture of paper.

The principal object of my invention is to provide a method for incorporating into paper filled with alkaline filler certain originally and normally soluble constituents in a substantially insoluble form.

An important object of my invention is the incorporation of sodium silicate in the form of an insoluble material into paper filled with alkaline filler.

A further object of my invention is to provide a process whereby fibrous material, sodium silicate, and alkaline filler are employed in the beater, and wherein alum is added to the paper mix at the wet end of the paper machine. I O

Other objects and advantages of my invention will become apparent during the course of the following description.

It is desirable at times in the papermaking operation to incorporate soluble material'into the fibrous mix, subsequently adding anagent serving mutually to react with the soluble material to form a substantially insoluble compound, which compound remains associated to a substantial degree with the papermaking ingredients, and thus becomes incorporated in the resulting paper. V

Such a soluble material is sodium silicate precipitated as by alum. This has been used,

for a long time in papermaking for a number of purposes, particularly for imparting snap and stiffness to a sheet of paper, reducing the fuzz and the like. There are a number of other desirable characteristics that the alum-sodium silicate precipltate imparts to the stock and the sheet into which the stock is made, a good summary of these being given on page 114 of Th. E. Blasweilers book on The Use of Sodium Silicate for the Sizing of Paper, translated by C. F. Cross, published by Constable & Co., Ltd., London, 1926.

The ordinary method of incorporating sodium silicate int-o paper is by the addition of sodium silicate in the beater, followed by the addition of alum in the beater, which serves to precipitate the alum-sodium silicate reaction product, which may be referred to as aluminum silicate without thereby being limited to any definite formula for this compound. Of course the order of addition of these materials may" be reversed, and sometimes the precipitation may be caused to take place in the presence of starch or other colloidal material to give a more finely dispersed precipitate. These and other variations are well known in the art.

The above method is entirely satisfactory when filler of the type of clay, talc, or the like vare used, but 'I have found in attempting to incorporate sodium silicate in this manner in paper in which alkaline filler was employed, that the stock and the paper made from such stock-possessed in only a minor degree or not at all the characteristics desired to be immachine, the e ect of the reaction product, 7

which is deteriorated even to the point of destruction by the alkaline filler,- being restored by adding a restoring agent such as alum to the mix atthe wet end of the paper machine. In the present application I disclose and claim a further discovery, namely that soluble material such as sodium silicate can be satisfactorily incorporated into paper filled with alkaline filler by treating a paper mix in amanner somewhat similar to that disclosed in my copending application referred to above, but omitting the addition of a precipitant in the beater and adding the precipig tant at or subsequent to the point where the mix is diluted prior to its passage on to the web-forming device of a paper machine.

In the preferred practice ofmy process I add to fibrous material in a beater or similar machine, or in a mixer or similardevice when abeater is not employed, alkaline filler of the character hereinafter referred to and a soluble material, such as sodium silicate. Other ingredients such as sizing material, for example. rosin size, coloring matter, or the like,

may be added if desired. In this connection 7 the process of my present invention may be used in conjunction with those disclosed in my copending applications Serial Nos. 304,172; 304,173; 304,174; 304,175; 304,177; all filed September 5, 1928. From the beater the mix is then passed through the usual preliminary papermaking procedure and at or subsequent to the point where the mix is diluted prior to the passage thereof 011 to a web-forming device of a paper machine, i. e. at the wet end of the paper machine, I add preferably continuously to the mix a suit,-

able precipitant, such as alum, preferably in manufacture of finished paper.

It is necessary as indicated to add the precipitant at or subsequent to the point of dilution of the mix,- as I have found that if it be added when the mix is in relatively concentrated condition, and particularly when the relatively concentrated mix is subjected to agitation as is normal in stock chests, the effect of the alum-sodium silicate precipitate is quickly deteriorated sometimes even to the point of complete destruction. The effect of the alum-sodium silicate precipitate even when the mix is in the diluted condition is gradually deteriorated, but is substantially unaffected within the time limits that the mix is maintained in the dilute state in the usual paper-making procedure. Moreover. al though agitation in the dilute state hastens to a certain extent the deterioration of this ef feet, the speed of deterioration is not nearly so pronounced as in the concentrated condition. and from a practical standpoint I have found that the agitation to which the diluted mix is subjected prior to delivery on to the webforming device does not deteriorate this effect to a suhst ant ial de ree. I

Of course the soluble material such as sodium silicate may he added at auv )oint prior to web t'orlnat ion other than in wheator. even after the addition of the alum at the wet. end of the paper machine. but e.\ )Nl: ments do not. indicate that any substantially better cll'cct from the ahun sndinm silicate precipitate is obtained thereby. and such addition thclel'ore can he considered the substantial equivalent of adding the sodium silicute in the heater.

'lhe alum solution need not be added di reel-l) to the lilo-oasmix. but can he added to the freshwater or white water. 0. g. tray water. with which the mix is diluted. If the alum ho added to the trav water, only a brief time interval should ela so before the so treated tray water is used or dilution.

In regard to the amount of sodium silicate used, this will be regulated by the intensity of the effect desired to be produced. The ran e from A; of 1 per cent. to 4 per cent. of 60 sodium silicate calculated on the total air dry weight of the material in the beater will be found to satisfy most requirements.

In regard to the amount of alum employed, it is desirable to use an amount equal to that which would give a slight acid reaction were the alum mixed alone with the sodium silicate. Owing to the fact that various samples of sodium silicate difi'er so widely in alkaline content, it-is best to determine in a preliminary test, by titrating a sample of sodium silicate with alum, how much alum it would take to bring the sodium silicate to this slightly acid reaction. If material other than alum is used, a suitable amount is somewhat more thanwill effect a maximum precipitation of the sodiumsilicate, as determined by titration ofa sample.

Inasmuch as the amount of precipitant used in the present process may be less than the combined amount of precipitant and restoring agent used in the process set forth in my eopending application Serial No. 319,719 filed November 15, 1928, therefore the process of the present invention results in a more economical operation, and also a simpler one.

. An illustrative furnish which may advantageously be used in practicing my invention 1s:

Illafmv'als added inbeater Pounds Fibrous furnish. (air dry basis), e. g.

sulphite and soda pulps 1700 Inorganic alkali metal salt. e. g. 60 B.

zlfohrl'ul mlu'cd to minproporta'on(dc/y and confin-umlslg on dilution V Pound! Procipitant. e. g. alum Another illustrative furnish is as follows: 7

Materials added in beater.

Material added to mix proportionately and continuously on dilution Pounds Precipitant, .e. g. alum 60 However, I do not by any means restrict my invention to the 'above formulae which are intended as illustrative only and not limiting, norto'any definite quantities of sodium silicate or ratio of sodium silicate to alum, as I have found that my invention may be satisfactorily employed with varying amounts of sodium silicate with a wide variation of the ratio of sodium silicate to alum, but of course from the standpoint of economy, I prefer to use the least amounts of sodium silicate and alum which experience indicates under given conditions will produce thedesired result.

I have found that sodium silicate is merely a representative of a class of substances which may be incorporated into aper in substantially the same manner. his class of substances consists of those inorganic alkali metal salts with a pH value greater than 7 .0, which are precipitable by material which depresses their hydroxyl' ion concentration. Sodium silicate has already been cited as one example of such a class of substances. An-

. other example issodium stannate.

As a precipitant for the sodium silicate or equivalent substance, I may use any material which depresses the hydroxyl ion concentration thereof in the place of alum, such as agitated in contact with freshly boiled dis tilled water, say for an hour, willimpart a pH value to such water greater than 7.0, that is, which will be on the alkaline side of the neutral point. Among fillers included in this'group may be mentioned calcium carbonate, of which lime mud from the causticizing process is one fo'rm;calcium carbonate magnesium basic carbonate employed in the paper. disclosed in my U.- S. Patent No. 1,595,416, issued August 10, 1926; calcium carbonate magnesium hydroxide disclosed inmy U. S. Patent No. 1,415,391, issued May 9, 1922; and other substantially water insoluble normal or basic carbonates of alka-- line earth metals, (which expression is herein intended to include magnesium), or compounds, double salts, or physically associated mixtures of these with one or more other acid soluble materials of a substantially water insoluble nature.

- By the term alkaline filler I also intend to include fibrous material and/or other material suc h' as paper coating constituents or the'like containing one or more compounds of the character referred to, such as old' papers like.

When I use the word paper herein, I use it in .the broad sense to include products of manufacture of all types and of all weights or similar papers, ,broke, or the and thicknesses, which contain as an essential constituent a considerable amount of prepared fibre and which are capable of being produced on a Fourdrinier, cylinder, or other forming, felting, shaping or molding machine.

By the term wet end of the paper machine I intend to include those instrumentalities employed inpaper manufacture by which and/or in whicha relatively concentrated paper mix is diluted, and treated, conveyed or fed up to the point of Web-formation, such as the mixing box, regulating and proportioning devices, rifilers, troughs, screens, head boxes, inlets, and the like, including also inst-rumcntalities used in the white water cycle.

While I have described in detail the preferred embodiment of my invention, it is to be understood that the details of procedure, the portions of ingredients, and the arrangement of steps may be Widely varied without departing from the spirit of my invention or the scope of the subjoined claims."

I claim: A

1. The method of incorporating into paper filled with alkaline filler an inorganic alkali metal salt with a pH value greater than 7.0, which is precipitable by -material which depresses its hydroxyl ion concentration, comprising mixing fibrous material, alkaline filler, and said alkali metal salt, adding a precipitant therefor under conditions favorin the minimizing of the time of contact of t e constituents of the mix, and thereafter making paper therefrom.

2. The method of. incorporating into paper 'filled with alkaline filler an inorganic alkali metal salt with apH value greater than 7.0, which is precipitable by material which,

depresses its hydroxyl ion concentration, com prising mixing fibrous material, alkaline. filler, and said alkali metal salt, adding a precipitant therefor under conditionsfavoring the minimizing of the intimacy and time of contact of the constituents of the mix, and thereafter making paper therefrom.

3. The method of incorporating into paper filled with alkali'ne filler an inorganic alkali metal salt with a pH value greater than 7.0, which is precipitable by material which depresses its hydroxyl ion concentration,comprising mixing fibrous material, alkaline filler, and'said alkali metal salt, adding a precipitant therefor at'the wet end of the paper machine, and thereafter making papertherefrom.

4. The method of incorporating into paper filled with alkaline filler an inorganic alkali metal salt with a H value greater than 7.0, which is precipita le by material which de presses its hydroxyl ion concentration, com- 5 prising mixing fibrous material, alkaline filler, and said alkali metal salt in a heater, adding a precipitant therefor at the wet end of the paper machine, and thereafter making paper therefrom.

5. The method of incorporating into paper filled with alkaline filler an inorganic alkali metal salt with a pH value greater than 7 .0, which is precipitable by material which depresses its hydroxyl iron concentration, comprising mixing fibrous material, alkaline filler, and said alkali metal salt, adding acidic material at the wet end of the paper machine, and thereafter making paper therefrom.

6. The method of incorporating into paper 20, filled with alkaline filler an inorganic alkali metal salt with a pH value greater than 7.0, which is precipitable by material which depresses its hydroxyl ion concentration, comprising mixing fibrous material, alkaline filler, and said alkali metal salt, adding a salt of a trivalent metal at the wet end of the paper machine, and thereafter making paper therefrom.

7. The method of incorporating into paper filled with alkaline filler an inorganic alkali metal salt with a pH value greater than 7.0, which is precipitable by material which depresses its hydroxyl ion concentration, comprising mixing fibrous material, alkaline filler, and said alkali metal salt, adding a salt of aluminum at the wet end of thepaper machine, and thereafter making paper therefrom.

8. The method of incorporating into paper 49 filled with alkaline filler an inorganic alkali metal salt with a pH value greater than 7.0, which is precipitable by material which depresses its hydroxyl ion concentration, comprising mixing fibrous material, alkaline 5 filler, and said alkali metal salt, adding alum at the wet end of the paper machine, and thereafter making paper therefrom.

9. The method of incorporating into paper filled with alkaline filler an inorganic alkali 5;) metal salt with a pH value greater than 7 .0,

which is precipitable by material which depresses its hydroxyl ion concentration, comprising mixing fibrous material comprising soda and sulphite pulp, alkaline filler, and

r? said alkali metal salt, adding a precipitant therefor at the wet end ofthe paper machine,-

and thereafter making paper therefrom.

10. The method of incorporating into paper filled with alkaline filler an inorganic c3 alkali metal salt with a pH .value greater than 7.0, which is proeipitable by material which depresses its hydroxyl ion .concentration, comprising mixing fibrous material comprising sodaand sulphite pulp and old paper stock, alkaline filler, and said alkali metal salt, adding a precipitanttherefor at the wet end of the paper machine, and thereafter making paper therefrom.

'11. The method of incorporating sodium silicate into paper filled with alkaline filler, comprising mixing fibrous material, alkaline filler, and sodium silicate, adding a precipitant therefor at the wet end of the paper ifnachine, and thereafter making paper thererom. 4

12. The method of incorporating sodium silicateinto paper filled with alkaline filler, comprising mixing fibrous material, alkaline filler, and sodium silicate, adding alum at the wet end of the paper machine, and thereafter making paper therefrom.

13. The method of incorporating sodium silicate into paper filled with alkaline filler, comprising mixing fibrous material, alkaline filler, comprising alkaline earth metal COIl] pound, and sodium silicate, adding alum at the wet end of the paper machine, and there-' after making paper therefrom.

14. The method of incorporating sodium silicate into paper filled with alkaline filler, comprising mixing fibrous material, alkaline filler comprising calcium carbonate, and sodium silicate, adding alum at the wet end of the paper machine, and thereafter making paper therefrom.

15. Themethod of incorporating sodium silicate into paper filled with alkaline-filler, comprising mixing fibrous material, alkaline filler comprising calcium carbonate and magnesium compound, and sodium silicate, adding alum at the wet end of the paper machine,

and thereafter making paper therefrom.

16. The method of incorporating sodium silicate into paper filled with alkaline filler, comprising mixing fibrous material, alkaline filler comprising 'calcium carbonate magnesium hydroxide, and sodium silicate, adding alum at the wet end of the paper machine, and thereafter making paper therefrom.

17. That step in a method of incorporating into a sized paper filled with alkaline filler an inorganic metal salt with a pH value greater than 7.0, which is precipitable by material which depresses its hydroxyl ion concentration, comprising adding at the wet end of the paper machine to a paper mix includkali metal salt, and sizing material, material which depresses the hydroxyl ion concentration of said alkali metal salt.

18. That step in a method of incorporating into a sized paper filled with alkaline, filler an inorganic metal salt witha .pH value" greater than 7.0, which is precipitable by material which depresses its hydroxyl ion concentration, comprising adding at the wet end of the paper machine to a paper mix including fibrous material, alkaline filler, said alkali metal salt and rosin size, material which depresses the hydroxyl ion concentration of said alkali metal salt.

19. That step in a method of incorporating into paper filled with alkaline filler an inorganic alkali metal salt with a H value greater than 7.0, which is precipitable by material which depresses its hydroxyl ion concentration, comprising adding a precipitant for said alkali metal saltat the wet end of the paper machine to a paper mix including fibrous material and alkaline filler.

20. That step in a method of incorporating into paper filled with alkaline filler an inorganic alkali metal salt with a pH value greater than 7 .0, which is precipitable by material which depresses its hydroxyl ion concentration, comprising adding a precipitant for said alkali metal salt at the wet end of the paper machine to a paper mix including fibrous material, alkaline filler, and said alkali metal salt.

21. That step in a method of incorporating sodium silicate into paper comprising adding a precipitant therefor at the wet end of the paper machine to a paper mix including fibrous material and alkaline filler.

22. That step in a method of incorporating sodium silicate into paper comprising ad ing alum at the wet end of the paper machine to a paper mix including fibrous material, alkaline filler, and sodium silicate.

23. That step in a method of incorporating sodium silicate into a sized paper filler with alkaline filler, comprising adding to a paper mix including. fibrous material, alkaline filler, sodium silicate, and sizing material, a precipitant for said sodium silicate and sizing material at the wet end of the paper machine. 24. That step in a method of incorporating sodium silicate into a sized paper filled with alkaline filler, comprising adding to a paper mix including fibrous material, alkaline filler, sodium silicate, and sizing material, alum at the wet end of the paper machine.

25. That step in a method of incorporating sodium silicate into a sized paper filled with alkaline filler, comprising adding/to a paper mix containing fibrous material, alkaline filler, sodium silicate, and rosin size, alum at the wet end of the paper machine.

26. That step in a method of incorporating sodium silicate into paper filled with alkal ne filler, comprising adding to a paper IIllX mcluding fibrous material comprising soda and sulphite pulp, alkaline filler, and sodium alum at the wet end of the paper machine. 1

27 That step in a method of incorporating sodium silicate into paper filled with alkaline filler, comprising adding to a paper mix containing fibrous material comprising soda and sulphite pulp and old paper stock, alkaline filler, and sodium silicate, alum at the wet end of the paper machine.

said

28. That step in a method of incorporating a precipitate of aluminum silicate into a paper filled with alkaline filler comprising ad alum at the wet ding end of the paper machine to a paper mix including fibrous material,

alkaline filler, sizing silicate.

29. That step in a method of incorporating a precipitate of aluminum silicate into a sized paper filled with alkaline filler comprising adding alum at the wet end of the paper machine to a paper mix including fibrous material, alkaline filler, sizing material and sodium silicate. v

30. That step in a method of incorporating a preciptate of aluminum silicate into a sized paper filled with alkaline filler comprising adding alum at the wet end of the paper machine to a paper mix including fibrous material", alkaline filler, rosin size, and sodium silicate.

In testimony whereof I afiix my signature.

HAROLD ROBERT RAFTON.

material and sodium 

